1. Field of the Invention
The present invention relates to a light emitting diode (LED) inspection apparatus and an LED inspection method using the same, and more particularly, to an LED inspection apparatus capable of determining whether an LED being inspected has a defect such as current leakage, without making physical contact with the LED, and an LED inspection method using the same.
2. Description of the Related Art
The recent improvements in luminous efficiency of a light emitting diode (LED) has expanded application fields of the LED from signaling to a lighting unit, a backlight unit (BLU) for a mobile phone, a light source of a large display device such as a liquid crystal display (LCD) and the like. This is due to the small power consumption and the long life of the LED, compared to related art lighting devices such as bulbs and fluorescent lamps.
The LED is manufactured by processes: growing, on a substrate, semiconductor layers of different conductivity types and an active layer activating light emission between the semiconductor layers, and forming an electrode on each of the semiconductor layers. The LED manufactured in this manner undergoes an inspection of its performance such as light-emission efficiency. Among performances being inspected, the leakage current is considered a factor that affects the reliability of an LED product because of its influence on the LED in terms of stability, life and performance deterioration.
To detect the leakage current, a process for inspecting the LED performance on a chip level is inserted in an LED manufacturing process. The equipment used for this inspection is called a prober, which can measure characteristics after a voltage is applied to an LED in a state where an electrical contact has been made between a transparent electrode and a bonding pad. That is, the prober measures an operating current and a voltage of the LED to which the voltage is applied, thereby inspecting electrical characteristics of the LED.
In the prober, an LED to be inspected on a wafer or chip level is fixed on an XY motion stage that can be moved forward, backward, left and right. A microscope is placed above the LED, and a probe serves as an electrode that applies a current/voltage to the LED. When an applied voltage is increased, an operating current of an LED also increases. Therefore, the leakage current causes the operating current to exceed a predetermined value. Thus, determination of a defective LED can be made by comparison with a voltage/current curve of a reference LED.
However, the inspection needs to be performed after the probe serving as an electrode physically contacts an LED to be inspected. The physical contact may damage the LED. If multiple samples are inspected, moving, contacting and measuring need to be repeatedly performed, undesirably increasing the inspection time. Also, an XY motion stage with high precision needs to be used because each sample needs to be moved according to a probe location.
Accordingly, there is a need for an apparatus that can inspect defects of LEDs with high efficiency, without degrading the performance of the LEDs.